Furnace and method of operating the same



April 1931- H. J. KERR 1,800,689

FURNACE AND METHOD OF OPERATING THE SAME Filed Aug. 16. 1927 /W J r J INVENTOR Patented Apr. 14, 1931 UNITED STATES PATENT OFFICE HOWARD J. KERR, F WESTFIELD, NEW JERSEY, ASSIGNOR TO THE .BABCOCK & WILCOX COMPANY, OF IQAYONNE, NEW JERSEY, A CORPORATION OF NEW JERSEY FURNACE AND METHOD OF OPERATING THE SAME Application filed August 18, 1927. Serial No. 213,234.

My invention more particularly relates to a furnace and method of operating the same wherein a movable fuel bed is fed into the furnace, in which air is passed through the major portion of the fuel bed and air at a lower temperature is passed through the feed end of the fuel bed.

My invention will best be understood by reference to the acompanying drawing show- 'ing in side elevation, partially in section, a

steam boiler and its setting and the associated parts, the drawing being somewhat diagrammatic.

I have illustrated my invention in con- 1 junction with a steam boiler, which may be of any desired construction, and in the illustrated embodiment of which I have shown onl a steam and water drum 10. The front wall of the setting is illustrated at 11, and

the rear wall thereof at 12, an ignition arch 13 being provided above the feed end of the device which moves the fuel bed into the furnace and which is here illustrated as a chain grate 14. A hopper 15 is provided in the usual manner for supplying fuel to the feed end of the chain grate.

Inthe embodiment of my invention illustrated, a forced air blast is supplied to the furnace by a forced blast fa'n 16 from which the air passes through a duct or passage 17 around the tubes 18 of an air heater 19, from the end of which the air is caused to pass through a duct 20 and distributed through passages 201 to the compartments 141 provided throughout the major portion of the chain gratefstoker and from which the air passes upwardly through the fuel bed. The temperature of the air passing over the tubes 0 of the air heater is raised by the gases from the combustion chamber 21 which, after passing over boiler heating surfaces, pass through the tubes 18 of the air heater.

v In the embodiment of my invention illus- 5 trated, the heated air is also supplied to the compartment 142 at the front or feed end of the stoker, the supply of heated air to this and the other compartments being controlled by dampers 22. F rbm the air heater, the

gases pass through a duct 23 to an induced draft fan 24 from which the gases pass to the stack 25.

In accordance with my invention, air at a lower temperature is passed through the fuel bedat the feed or entrance end thereof than that which is passed thfough the remaining major portion of the fuel bed.

In the embodiment of my invention i1lustrated, heated air may be forced into the front compartment 142 where other colder air is mixed therewith. For this purpose, the cold air may be forced to the compartment 142 by the blower 16, a duct 26 communicating with the duct 17 between the blower 16 and the air heater 19. The amount of cold air introduced to the front compartment 142 may be regulated by a damper 27 so that both the heated air and the cold air are introduced in regulated amounts, and the air passing from the compartment 142 through the entrance or feed end of the fuel bed may have any desired temperature.

By shutting the first damper 22 at the left of the figure and at the entrance end of the fuel bed and opening the damper 27, all of the air supplied to the first compartment 142 of the stoker would be cold air. By varying the positions of the dampers 22 and 27, the temperature of the mixture of the heated and the cold air in the compartment 142, and hence the temperature of air passing through the feed end of the fuel bed, may be kept at any desired value.

Where all of the air forced into a chain grate stoker has been heated, it has in some cases and with certain kinds of coal caused an overheating of the entrance or feed end of the fuel bed with the result that the fuel bed at this portion becomes matted down so as to become more or less impervious to the air, and this action may be partially, at least, due to coking. Whatever the cause is, however, I have found in practice that the use of air at a lower temperature at the entrance or feed end of the fuel bed than in the remaining portion thereof has resulted in bet ter combustion and, therefore, better efficiency of the furnace with certain types of coal.

I claim:

1. The method of operating a furnace provided with achain grate through which a forced blast of preheated air is passed which consists in mixing cooler air with the heated air at the entrance end of the chain grate.

2. The method of operating a furnace into which a fuel bed is movable and through i which preheated combustion air is passed which consists in mixing a regulated amount of cold air with the heated air at the entrance end of the fuel bed. V

3. The method of operating a furnace in which a fuel bed is movable which consists in preheating combustion air, forcin said preheated combustion air through a p urality of sections of the fuel bed, and forcing relatively colder air through the entrance section of said fuel bed.

4. The method of operating a furnace in which a fuel bed is movable which consists in preheating combustion air, forcin said preheated combustion air through a plurality of sections of'the fuel bed and mixing cold air with the'preheated air and then forcing the mixed air through the entrance section of said fuel bed.

5. The method of operating a furnace in which a fuel bed is movable which consists in preheating combustion air, forcing said preheated combustion air through a plurality of sections of the fuel bed, mixing cold air with the preheated air and thenforcing the mixed air throughthe entrance section of said furnace, and regulating the relative amounts of hot and cold air insaid entrance section.

6. In combination, a furnace, means for moving a fuel bed into the same, means for supplying combustion air to and passing it said combustion air, and means for mixing cooler air with said combustion air at the it through the fuel bed, means for utilizing the waste heat gases from the furnace for preheating the combustion air for the fuel ed, and means for mixing cooler air with said combustl'onair at the entrance endof the furnace.

9. In combination, a furnace, means for f moving a fuel bed into the same, an air through the fuel bed, means for preheating HGWARD J. KERR.

heater, means for passing the spent gases from the furnace through said air heater, a

forced blast device for forcing air through I 

